U.S. patent application number 12/030277 was filed with the patent office on 2009-08-13 for method to detect and locate a breach in vertical or horizontal intersections in a membrane of a roof.
Invention is credited to David E. Vokey.
Application Number | 20090199506 12/030277 |
Document ID | / |
Family ID | 40937701 |
Filed Date | 2009-08-13 |
United States Patent
Application |
20090199506 |
Kind Code |
A1 |
Vokey; David E. |
August 13, 2009 |
METHOD TO DETECT AND LOCATE A BREACH IN VERTICAL OR HORIZONTAL
INTERSECTIONS IN A MEMBRANE OF A ROOF
Abstract
A defect in a horizontal or vertical seam at the edge of a roof
membrane is detected by applying a DC voltage between the roof deck
a probe in the form of a flexible wetted sponge and wiping the
sponge probe over the seams. The current to the probe is detected
and indicated to the operator so that the operator may determine a
maximum current at the defect. The receiver provides an audible
signal emitter to the operator and includes a calibration circuit
arranged to automatically maintain, despite changes in voltage
applied between the roof deck and the peripheral conductor, a "0"
set calibration point so as to indicate at the calibration point
when zero difference in voltage is detected. Conductors can be
applied to the membrane to define an area to be tested within the
conductors.
Inventors: |
Vokey; David E.; (Sidney,
CA) |
Correspondence
Address: |
ADE & COMPANY INC.
2157 Henderson Highway
WINNIPEG
MB
R2G1P9
CA
|
Family ID: |
40937701 |
Appl. No.: |
12/030277 |
Filed: |
February 13, 2008 |
Current U.S.
Class: |
52/741.3 |
Current CPC
Class: |
E04D 13/006 20130101;
G01M 3/16 20130101 |
Class at
Publication: |
52/741.3 |
International
Class: |
E04G 23/03 20060101
E04G023/03 |
Claims
1. A method of locating a defect in a a roof membrane covering a
roof deck, the method comprising: providing an electrical
connection to the roof deck; providing a sensor probe formed of a
flexible pad of a material arranged to carry a conductive liquid;
wherein the probe is mounted on an insulated handle such that the
probe can be pressed against the surface being tested by manual
operation of the handle by the operator while insulating the
operator from the conducting probe; applying a voltage between the
roof deck and the sensor probe; engaging the probe with the roof
membrane such that the conductive liquid is wiped over the
membrane; detecting the current between the probe and roof deck;
and providing to an operator controlling the location of the probe
a signal indicative of the current so as to allow the operator to
locate the defect by moving the probe to different locations.
2. The method according to claim 1 wherein the current is detected
by a receiver which includes a variable sensitivity and an analog
display for the differences in current detected.
3. The method according to claim 1 or 2 wherein the current is
detected by a receiver which provides an audible signal emitter
such that a signal indicating the maximum leakage current detected
can be determined audibly.
4. The method according to claim 3 wherein the audible signal
emitter includes a voltage to frequency converter.
5. The method according to any one of claims 1 to 4 including
generating a potential difference between shielding conductors
adjacent the probe and the roof support deck such that currents
generated through the membrane are drawn to the shielding
conductors so as to create a shielding zone around the probe.
6. The method according to claim 5 wherein the shielding conductors
comprise un-insulated wire or metal foil on the membrane at the end
or ends of the shielding zone.
7. (canceled)
8. The method according to claim 1 wherein the current is detected
by a receiver which includes a calibration circuit arranged to
automatically maintain, despite changes in voltage applied between
the roof deck and the peripheral conductor, a "0" set calibration
point so as to indicate at the calibration point when zero
difference in voltage is detected.
9. The method according to claim 8 wherein the calibration circuit
includes an operational amplifier arranged to provide a circuit
common ground from an input tied to the half the supply voltage
point between +V and -V through equal value dividing resistors.
10. The method according to claim 1 wherein the handle comprises a
transverse bar at the rear of the probe.
11. The method according to claim 1 wherein the handle comprises an
elongate pole extending from the rear of the probe.
12. The method according to claim 1 wherein the pad is formed of
sponge.
13. A method according to claim 1 wherein a part of the roof is
tested by: providing a first conductor arrangement for engaging the
roof above the membrane; providing a return conductor arrangement
for electrical connection to the support deck; generating an
electrical potential between the first and return conductor
arrangements; mounting the first conductor arrangement on a
carriage which can be moved over the roof so as to scan the first
conductor arrangement over selected areas of the roof while the
first conductor arrangement remains in contact with the roof as the
carriage is moved; sensing the current flowing from the roof
support deck to the first conductor arrangement; and detecting the
changes in current as the first conductor arrangement is scanned
over the selected areas of the roof to locate the leak in the
membrane; so that only remaining parts are tested using the
probe.
14. The method according to claim 13 wherein the carriage is
mounted on roller wheels for carrying the carriage in rolling
movement over the roof.
15. The method according to claim 13 wherein the carriage includes
a handle such that the carriage can be manually rolled across the
roof.
16. The method according to claim 13 wherein the first conductor
arrangement comprises at least one conductive component arranged
for engaging the roof and for sliding over the roof while in
contact therewith.
17. The method according to claim 16 wherein the conductive
component comprises a conductive brush.
18. The method according to claim 13 wherein the first conductor
arrangement includes first and second conductor members which are
electrically isolated from each other, wherein the electrical
potential is arranged to be applied between both the first and
second conductor members of the first conductor arrangement and the
roof support deck and wherein the current flowing from the roof
support deck to the first and second conductor members is
independently sensed to detect the changes in current as the first
conductor arrangement is scanned over the selected areas of the
roof to locate the leak in the membrane.
19. The method according to claim 18 wherein there is provided a
measuring and switching circuit which includes two independent
leakage current detection components sharing a common power supply
source.
20. The method according to claim 18 wherein the first conductor
member is an inner member and the second member is an outer
shielding member surrounding the first inner member with both the
first inner member and the second outer member engaging the roof.
Description
[0001] This application is related to U.S. application Ser. No.
12/020,935 filed 28.sup.th Jan. 2008 and entitled A METHOD AND
APPARATUS TO DETECT AND LOCATE A BREACH IN A ROOF MEMBRANE.
[0002] This application is related to U.S. application Ser. No.
11/949,437 filed 3.sup.rd Dec. 2007 and entitled METHOD AND
APPARATUS TO DETECT AND LOCATE DAMAGE AND BREACHES IN ROOF
MEMBRANES.
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a system for testing roof
membranes to detect and locate damage and moisture penetration in
the vertical and corner intersection surfaces of roof membranes. It
has particular application to testing the integrity of vertical and
sloped surfaces of residential and commercial buildings.
[0004] The failure to detect, find, and correct minor roof
deterioration in the earliest stages is considered the greatest
cause of premature roof failure. This is particularly true of
roofing materials applied on low-slope or flat roofs. Costly
roofing problems are often the result of design deficiencies or
faulty application of the roof system. Even when properly designed
and applied, all roofing materials deteriorate from the contraction
and expansion of roof decks and natural aging processes.
[0005] Several methods have been used to try and locate roof leaks
after they have occurred. Electric capacitance meters identify
leaks using a low-frequency method that measures dielectric
constant changes in the roofing material as a result of moisture
below the membrane. Infrared cameras allow technicians to scan roof
surfaces for temperature differentials that signify moist areas
through changes in thermal conductivity or evaporation. These
methods are typically used in forensic analysis only after
significant leakage has occurred.
[0006] Electric field mapping uses a wire loop around the perimeter
of the roof surface to introduce an electric potential between the
structural deck and a selected roof area which is sprayed with
water. The electric field potential caused by a conductive path to
any roof membrane damage is then located using a voltmeter and a
pair of probes.
[0007] U.S. Pat. No. 4,565,965 issued Jan. 21, 1986 to Geesen
discloses an electric field mapping arrangement for detecting leaks
in flat roofs in which electrical pulses are transmitted through
the moisture in the leak to the roof edge. The roof is then scanned
by a pulse sensor and hand-held probe rods to find the leak by
locating the maximum amplitude. The disclosure of this prior patent
is incorporated herein by reference.
[0008] The method as described by Geesen is applicable on
horizontal low slope or flat surfaces only and does not allow the
testing of corner or wall intersection areas.
SUMMARY OF THE INVENTION
[0009] It is an object of the present invention to provide an
apparatus and method for the detection and location of moisture
penetration at horizontal and/or vertical intersections and on the
vertical or sloped surfaces of roof membranes.
[0010] According to a first aspect of the invention there is
provided a method of locating a defect in the vertical or
horizontal intersections of a roof membrane, the method
comprising:
[0011] providing a ground connection to the roof deck
[0012] applying a voltage between the roof deck and a wet sponge
like sensor probe;
[0013] using a wet sponge like sensor probe and engaging the probe
with the roof membrane at vertical seams and joints on the membrane
to detect a leakage signal generated by current flowing between the
roof deck and the sponge like probe;
[0014] providing a receiver which acts to detect the leakage
current between the probe and wall or roof deck;
[0015] the receiver being arranged to provide to an operator
controlling the location of the probe a signal indicative of the
leakage current so as to allow the operator to locate the defect by
moving the probe to different locations;
[0016] wherein the probe is mounted on an insulated rigid base with
a suitable handle or pole such that the wet sponge like probe can
be pressed against the surface being tested while insulating the
technician from the conducting probe.
[0017] The voltage applied is preferably a DC voltage but an AC
signal could also work. There are several ways to implement an AC
detection circuit and one could overcome any potential DC offsets
from half-cell potentials. However DC works well and is easier. The
above patent of Geesen, the disclosure of which is incorporated
herein by reference, proposes an arrangement by which an AC signal
can be used and a person skilled in the art can adapt such an
arrangement to the present construction.
[0018] Typically, the test described and claimed herein is carried
out on a membrane before any overburden such as gravel or pavers
are placed on top. In this case all the seams. near the wall/roof
deck interface and on the vertical portions of the parapet are
tested using the technique. After this test the carriage
arrangement described herein is used to test the main area of the
horizontal roof membrane.
[0019] The further technique of the framed probes described herein
is used when the deck is covered with an overburden or garden and
the membrane is covered.
[0020] Preferably the receiver includes a variable sensitivity and
an analog display for the differences in current detected.
[0021] Preferably the receiver provides an audible signal emitter
such that a signal indicating the maximum leakage current detected
can be determined audibly.
[0022] Preferably the audible signal emitter includes a voltage to
frequency converter.
[0023] If required there may be provided an external connection to
the receiver common ground to form an external grounding or
screening connection to allow electrical isolation of the area
under test.
[0024] Thus un-insulated wire or metal foil can be placed on the
membrane at the end or ends of the area to be tested;
[0025] In this way, the un-insulated wire or metal foil connected
to the common ground by a connecting lead acts so as to block and
ground any leakage current outside of the area under test so that
the probe will only detect any leakage current in the test
area.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] One embodiment of the invention will now be described in
conjunction with the accompanying drawings in which:
[0027] FIG. 1 is an isometric view of a frame mounted leak location
system on a roof deck.
[0028] FIG. 2 is a circuit schematic of the receiver of FIG. 1
which includes an auto-zeroing receiver system and an audible
alert.
[0029] FIG. 3 is an isometric view of a leak detection probe on a
vertical seam of a roof membrane.
[0030] FIG. 4 is an isometric view of the leak detection probe on a
horizontal seam with isolating conductors applied.
[0031] FIG. 5 is an isometric view of a roof membrane on a roof
deck including a basic illustration of a carriage arrangement for
use in carrying out a test on the main body of the membrane.
[0032] FIGS. 6A, 6B and 6C show respectively a top plan view, a
bottom plan view and a front view of the carriage and sensing
system for use in the general method of FIG. 5.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] The following description is taken from the above
application and is included to ensure description of the complete
system with which the present invention can be used.
[0034] The operation of the horizontal roof membrane leak location
system is shown in FIG. 1. A bare conductor 3 is placed in a closed
loop on top of the roof membrane area to be tested. A DC power
source 4 is connected between the roof deck and the energizing
conductor 3 by a grounding cable 6 connected to a building ground
point 7 on the roof deck and an energizing cable 5 connected to the
loop conductor 3. The surface of the roof membrane is then sprayed
with water so as to dampen the entire area 1 under test.
[0035] A probe mounting frame 8 with a receiver 9 attached to the
frame is positioned within the area to be tested. Two insulated
conducting probes 11 carried on the frame are connected to the
input of the receiver 9, mounted on the frame, by two insulated
connecting cables 10. A headphone and connecting cable 12 is
plugged into the audio output jack on the receiver 9. The frame is
a fixed structure which provides two legs 8A and 8B at fixed
separation and position to hold the probes at a fixed spacing. The
legs are carried on a handle 8C which can be grasped by a single
hand of the operator to simultaneously manipulate the position and
orientation of the frame and the probes.
[0036] Thus the frame includes a pair of upstanding legs onto a
lower end of each of which a respective one of the probes is
mounted so as to project downwardly therefrom. The frame includes a
center handle portion between the legs.
[0037] An electrical circuit is formed between the roof deck via
the building ground 7 and the energizing cable 3 through any roof
membrane defect 2 which provides a conductive path through the
membrane. With the roof circuit energized, the mounting frame 8 is
positioned on the roof membrane and the probes 11 brought into
electrical connection with the roof membrane so that current flows
to the two probes.
[0038] It will be appreciated that the amplitude of the current
decreases along any line extending from the defect to the
peripheral cable 3.
[0039] The voltage connected between the roof deck and the
peripheral conductor is constant so as to generate a constant
current flow rather than the use of pulses which generate a varying
current due to the charging current rush at the beginning of every
pulse. The difference between the currents detected by the two
probes is at a maximum when a line 11A joining the probes 11 is
aligned with the defect. The current is at a maximum when the
probes are closest to the defect.
[0040] With the probes fixed on the frame 8, the frame is rotated
by the operator until the maximum difference between the two
currents is detected to provide a maximum pulse rate in the
headphones 12 which corresponds to a maximum reading on the signal
level meter 9. In this position, the operator knows that the line
11A joining the probes is aligned with the defect. The mounting
frame is thereby brought into directional alignment with the
current 13 from the defect so as to indicate the direction to the
location of the defect 2. The mounting frame is then advanced in
steps along that line 11A until a maximum signal level and audible
pulse rate is achieved thus indicating the actual location of the
defect.
[0041] The schematic diagram for the receiver unit is shown in FIG.
3. The two mounting frame probes 11 are connected by the insulated
cables 10 to the respective input terminals 23 and 24. One side 23
is connected to the negative summing input of a first stage op-amp
28 through a resistor R1. The other side 24 is tied to circuit
common. Diodes D1 and D2 provide input protection. The gain of the
first stage op-amp is set by resistor R2 and potentiometer P1 while
capacitor C1 filters out any unwanted noise.
[0042] The output of the first stage op-amp 28 is tied to the input
of a second stage op-amp 29 through a resistor R6. Resistors R6 and
R8 set the gain of the second stage op-amp 29 to unity. The
positive summing input of the second stage op-amp 29 is tied to
common through a resistor R7.
[0043] A voltage-to-frequency converter 32 has an input which is
connected to the output of the second stage op-amp 29. The output
of the V to F converter 32 is applied to the input of an audio-amp
34 through a volume control 33. The audio output of amp 34 is
connected to the headphones 12 or to a speaker 24.
[0044] The output of the second stage op-amp 29 is connected to
voltage limiting diodes D3 and D4 through a resistor R9. A signal
level meter 31 is connected in series with a scaling resistor R10
across the diodes D3 and D4.
[0045] In order to avoid the need for zero offset adjustment of the
meter circuit 31 as the supply voltage V changes, there is provided
a circuit component which provides self adjustment of the common
ground G of the main circuit connected to the op-amps 28 and 29.
Thus the positive summing input of a third op-amp 30 is tied to the
half the supply voltage point between +V and -V through equal value
dividing resistors R4 and R5. The negative summing input and output
port of op-amp 30 forms the circuit common G. In this way there is
automatic adjustment of the circuit ground so that the meter is
always centered at zero voltage difference between the probes and
the meter moves away from the center position when a current
difference is detected.
[0046] The above technique of the frame mounted probes is typically
used when the deck is covered with an overburden or garden and the
membrane is covered.
[0047] Turning now to the arrangement shown in FIGS. 3 and 4, the
operation of the vertical roof membrane leak location system is
shown in FIG. 3. The horizontal roof membrane 51 has a vertical
membrane 52 at a roof parapet 52A. The receiver 54, which is of the
construction and arrangement previously described, is operated to
apply the positive side of the power supply to a building ground
point 56 through a connecting cable 55. A connecting cable 57 and
headphones 58 provide the audible output signal from the receiver
54.
[0048] In the example in FIG. 3, a sensor 59 in the form of a wet
sponge is held against a seam on the vertical membrane. A
connecting cable 60 ties the conductive wet sensor 59 to the input
of the receiver 54. Moisture in the sensor 59 makes electrical
contact with the membrane. Any breach in the vertical portion of
the membrane will result in a conductive path forming through the
breach to the parapet wall. A fault current will flow from the
positively grounded building 56 through the breach to the wet
sensor 59 and connecting cable 60 into the input of the receiver
54. The detection circuit of the receiver 54 as described above
will generate an audible signal and meter deflection in response to
the leakage current.
[0049] The same probe can be wiped over a horizontal seam at an
edge of the roof.
[0050] The schematic diagram for the receiver unit 54 is shown in
FIG. 2. The building ground is connected to the positive supply via
the ground jack 26. The sensor 59 is connected via a cable 10 to
the negative summing input of the first stage op-amp 28 through the
input jack 23 and current limiting resistor R1. Diodes D1 and D2
provide input protection. The gain of the first stage op-amp is set
by resistor R2 and potentiometer P1 while capacitor C1 filters out
any unwanted noise.
[0051] The output of the first stage op-amp 28 is tied to the input
of the second stage op-amp 29 through a resistor R6. Resistors R6
and R8 set the gain of the second stage op-amp OA2 to unity. The
positive summing input of the second stage op-amp 29 is tied to
common through a resistor R7.
[0052] The voltage-to-frequency converter 32 has an input which is
connected to the output of the second stage op-amp OA2. The output
of the V to F converter 32 is applied to the input of the audio-amp
34 through a volume control 33. The audio output of amp 32 is
connected to the headphones 58 or to a speaker 35.
[0053] The output of the second stage op-amp 21 is connected to
voltage limiting diodes D3 and D4 through a resistor R9. A signal
level meter 31 is connected in series with a scaling resistor R10
across the diodes D3 and D4.
[0054] The sensor 59 comprises a sponge 65 mounted on a backing
plate 66 carried on an insulating handle 67. Thus the contact from
the cable 60 is connected to the conductive plate 66 for
communication of current through the moisture in the sponge.
However the operator moving the sensor is isolated from the current
by the to insulated handle 67.
[0055] The handle can comprises a simple transverse bar at the rear
of the probe or the handle can comprise an elongate pole extending
from the rear of the probe allowing the operator to stand and wipe
the probe over seams from a standing position.
[0056] The contact portion of the sensor 59 can comprise any
flexible material which can wipe over an area to be sensed and
provide contact between the material and the membrane over the
whole area of the material while carrying moisture into contact
with the membrane. Thus the material can be a sponge or can be a
fabric such as felt or can be other materials which have the
required characteristics of carrying the liquid into contact with
the membrane and sufficient flexibility to deform slightly where
required to remain in contact with the membrane over changes in
surface height and over changes of angle.
[0057] As the peripheral conductor 3 of FIG. 1 as no effect in
generating a potential difference in the area of the parapet 52A,
this arrangement uses current communicating directly between the
roof deck and the sponge sensor and acts to measure the absolute
value of that current against a fixed comparison value provide at
COM terminal 24 which is connected to the positive input of the
amplifier 28.
[0058] Thus the sponge sensor acts to apply moisture to the
membrane to create the conductive circuit and acts as a sensor to
detect the value of the current so caused. It will be appreciated
that the current will vary as the sensor is moved closer to a
breach from a zero current where there is no breach to a maximum
directly at the breach. The comparison with the fixed value thus
locates this maximum which is communicated to the operator either
using the meter 31 or the headphones 58.
[0059] In certain situations a conductive path will exist beyond
the area under test due to extensive wetting of the membrane. In
FIG. 4 a method to isolate the area under test is illustrated. A
horizontal seam 73 next to the parapet wall 72A is shown with a
water path 71 extending beyond the test area. A metallic strip 72
is placed across the water path 71 on one end of the area to be
tested and a second metallic strip 73 placed across the other end
of the area to be tested. The metallic strips are connected to the
circuit common ground via cables 74 and 75. Any fault current
flowing along the water path from membrane breaches outside of the
test area is isolated by the metallic strips thereby isolating the
test area.
[0060] Typically, the test described above is carried out on a
membrane before any overburden such as gravel or pavers are placed
on top. In this case all the seams. near the wall/roof deck
interface and on the vertical portions of the parapet are tested
using the technique.
[0061] After this test, the carriage arrangement described below is
used to test the main area of the horizontal roof membrane.
[0062] The overall arrangement of the carriage arrangement can best
be seen with reference to FIG. 5. A roof membrane 62 is illustrated
which is applied as a direct covering layer over a concrete roof
deck 61. The deck is typically of concrete to but can be of any
suitable material to provide the necessary structural strength and
can be steel or wood. The membrane is an impervious material such
as plastics and is sealed at any joints to provide a continuous
water barrier over the roof deck. This barrier is intended to
provide the leak prevention and any penetration therein caused by a
puncture or faulty seal or by wear can allow the moisture to
penetrate to the deck where it can cause damage or can continue
into the structure to cause damage to internal structures.
[0063] A defect in the membrane 63 allows water 4 to intrude and
forms a conductive path to the roof deck. The conductive outer 67
brushes and inner 68 brush are placed on the top surface of the
membrane 62 with the outer perimeter conductive brushes 67
surrounding the inner brush 68. The brush sets are positioned so as
to be in intimate contact with the wetted surface 64 of the test
area. The outer sweep detection circuit 65 and inner sweep
detection circuit 66 which share a common power supply are
connected to the outer brush set 67 and inner brush set 68
respectively with the common positive side of both connected to a
grounding point 69 on the deck.
[0064] A DC potential is applied between the roof deck 61 and the
wetted area 64. At the membrane damage site 64 there is a
conductive path through the membrane and a leakage current 70
travels through the damage point and back to the outer conductive
brush 67. The return current picked up by the outer brushes is
measured and displayed on the outer sweep circuit 65. As the outer
brush perimeter surrounds the inner brush sensor, very little of
the return current reaches the inner brush 68. The sweep system is
then moved forward over the membrane towards the defect and when
the outer brush passes over the damage site, the inner brush picks
up the return current and provides a visual and audible alarm. The
damage site is thereby located.
[0065] The detector circuit is substantially as shown and described
above.
[0066] The mechanical arrangement of the apparatus is illustrated
in FIGS. 6A, 6B and 6C. A horizontal platform or carriage 80 with a
flat top wall and a depending side wall 85 forming four sides of a
rectangular carriage. The carriage is carried on four swivel wheels
or casters 81 attached to the top plate by mountings 86. The
carriage supports an outer brush assemblies defined by two parallel
front and rear brushes 82 and two parallel side brushes 87, thus
defining a rectangular outer area just inside the outside wall of
the carriage. Inside the outer rectangular area is provided a
single transverse brush defining an inner brush 83. Vertically
floating brackets 84 position the outer brushes and allow vertical
movement of the brushes as the platform travels over the membrane
surface. Similar brackets 88 carry the inner brush. The brushes are
formed as a strip from conductive bristles carried on a base so
that the base can float upwardly and downwardly from pressure of
the roof against the tips of the bristles so that a constant
electrical contact is maintained with the roof.
[0067] A simple manually graspable handle assembly 90 is attached
to brackets 89 on the top plate of the carriage. The sweep circuits
are mounted in a housing 91 and attached to the handle 90 assembly
at a position below a top hand rail of the handle assembly.
* * * * *